It is general practice to use an automatic developing machine for developing a large amount of photosensitive lithographic printing plate precursors (hereinafter referred to as "PS plates").
The automatic developing machines typically include a device for the horizontal conveyance of PS plates, a developer tank and a spray device. The exposed PS plates are generally developed by spraying a developer, which has been supplied to a spray nozzle using a pump, upon horizontally conveyed exposed PS plates. Another type of automatic developing machine is also known where PS plates are dipped and conveyed through a developing tank, containing a developer by using a liquid guide roll or the like.
In the above processes, the developer is typically circulated through the automatic developing machine for repeated use for economical reasons. Therefore, the concentration of the light-sensitive layer components which are dissolved in the developer gradually increase thereby adversely affecting the ability of the developer to perform its function and causing a buildup of refuse or sludge in the form of precipitates in the developer. Furthermore, when an alkaline developer is used, carbon dioxide from the air may be absorbed thereby causing deterioration of the developer.
In addition to the above-mentioned problems relating to the deterioration of the developer solution, the machine itself can be stained by scattered liquid from the spray. Therefore, frequent exchange of the developer and washing of the automatic developing machine is required.
In an effort to overcome the above-described problems, a developer-replenishing system has been proposed, in Japanese Patent Application (OPI) Nos. 115039/80 and 95349/83 (the term "OPI" as used herein means a "published and unexamined Japanese patent application") for a circulation-system development of large numbers of PS plates, whereby a stabilized developer can be maintained for long periods of time. However, this system also is very complicated in that it requires careful control and maintenance of the replenishing device.
Methods for overcoming the above-mentioned problems associated with systems where large amounts of a developer are circulated and re-used in an automatic developing machine, have also been proposed in Japanese Patent Application (OPI) Nos. 29505/73 and 32044/80 and U.S. Pat. No. 4,222,656. In these methods a predetermined amount of fresh developer is supplied to the exposed surface of a PS plate. After development, the developer is then removed and disposed of (this type of systems being referred to as a "disposable development system" hereinafter).
In the disposable development system, the amount of a developer to be maintained on the PS plate for a predetermined period of time, may be kept to a minimum. Unfortunately, the developer is often uneven thereby causing development unevenness. In this regard, various attempts to overcome this problem have been made such as the use of larger amounts of the developer supplied to the PS plates, and evening the developer on the surface of the PS plates with a brush or sponge. However, the use of larger amounts of developer than the minimum amount necessary for development becomes necessary, thus unfavorably elevating the processing costs.